CODEWITHSUNDEEP
sqlitecastinghexascii
taz
taz

Reputation: 1526

Convert hex to text using SQLite

I am trying to convert from a string representing hex data to the textual encoding (ASCII, UTF-8, etc.) of the hex data using purely SQLite language. Essentially I want the functionality of the X'[hex]' syntax, but applied to a programmatically derived hex string.

I want, for example, select X(hex_data_string) from ..., which is not legal SQLite syntax.

Obviously in the above snippet, I would not necessarily be able to output the data if it was not in a valid textual encoding. That is, if hex_data_string contains control chars, etc., the X() should fail in some way. If this is possible, there would have to be a default character encoding or the desired character encoding would have to be specified somehow.

I am not asking about how to retrieve the hex data string value from the SQLite database and then use C or some other facility to convert it. I am trying to perform this conversion in pure SQLite because I have queries that I check which return a text representation of hex characters representing binary data. Most of the binary data is ASCII, so I want to be able to quickly view the content of the binary data in my query output when applicable.

Intuitively, I figured this could be accomplished by casting the hex data string to a blob and using hex() but that still returns the hex data string.

Any ideas?

Possible duplicates:

SQLite X'...' notation with column data

sqlite char, ascii function

Upvotes: 4

Views: 14937

Answers (3)

Mladen Mihajlovic
Mladen Mihajlovic

Reputation: 6435

This is quite old but I was looking for the same thing so I thought I'd post:

It seems you can just cast hex data as a varchar to convert it to ascii.

ie: select cast(data as varchar) from some_table will return a string representation of a binary field (data).

Upvotes: 8

Chris Werner
Chris Werner

Reputation: 1386

This will not be fully useful since it can't really be used inline, but I have done this in the past when I just wanted to convert one row of data and not create/find another utility.

WITH RECURSIVE test(c,cur) as (
     select '','686F77647921'
   UNION ALL
    select c || char((case substr(cur,1,1) when 'A' then 10 when 'B' then 11 when 'C' then 12 when 'D' then 13 when 'E' then 14 when 'F' then 15 else substr(cur,1,1) end)*16
               + (case substr(cur,2,1) when 'A' then 10 when 'B' then 11 when 'C' then 12 when 'D' then 13 when 'E' then 14 when 'F' then 15 else substr(cur,2,1) end)),
substr(cur,3)
from test where length(cur)>0
)
select * from test

Upvotes: 2

CL.
CL.

Reputation: 180070

This is not possible in pure SQLite.

As an embedded database, SQLite is designed to provide only pure database functions, and leave the program logic to the the application. You are supposed to retrieve the hex data string value from the SQLite database and then use C or some other facility to convert it.

If you control the program you're running the queries in, you could install a user-defined function that does this conversion.

Upvotes: 1

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